The separation of plutonium from uranium and fission products



Oct. 7, 195

G. E. B'OYD ET AL SEPARATION OF PLUT'ONIUM FROM URANIUM AND FISSION PRODUCTS Filed Aug. 29, 1944 Z72 Jzz fans: 61907 United States Patent.v

j rrrnsEnARArroNbFrLU'roNwMrRor/r i George:EuBoydnArthurcWi AdamsonnandzJack :Schubut; ak:1 g ,Jenn;LandEdrvin ;RR sse !,fch ca w l'er-assi nprs er i e; pi tedistets a i m as r entedbx henited tatesAt icEn r y:Commission Applichtion -August2934944; Serial we; -ss1-, 734- (ch sm- 4 D'E TB QDU S.

" at os f ea etai ed: pro s mbo y ng e nv on-1 e e e-r na ab g n ta e a re u t en p n-finer nvention ras-r ho ebyw in -rv "In; the following; description, thewisotope ofre lernent; 93;having a mass Of-,239,; is rrefer-red to as 93 9: and-the; isotope'aof element 94fhaving ;-a mass ofe23-9eis refierred to as -94 Elemen t= 94 rmay-also be designated as;plutonium, symbol -Pu.- Reference'herein to-any ofi--the elements iseto be understood as, denoting the, element generically, whether in its free state oriin the for rrnof 11a.

compound, unless indicatedvotherwise by, the. ,context:

Neutron-irradiateduraniumtmay be preparedt.by re, acting, uranium,with-neutrons frorn any,suitable neutron source; V

Neutron irrradiation of uranium; produces UvmIwh ich has ,a. half=li-fie .of-,i 23 minutes and .b y beta decay; becomes 93 ThiseIomenLhas a half-life of ,2,3,days and b y, e atdeqayt e mew' eutr nz t ated" ranium. contains 9 3 94 1anda large nurnber of fradioactiye fission products producedflby reaction, of neutrons on fissionable atoms, snch as; U whic'h'is present -in urani um from natural sources. It also contains 'minorarnounts ofotherprodn'cts such as UX and '=UX Inasmuch as the 93 and 94 content of neutron-irradiated uranium is produced inraccordance@ with the neutron density P- of exposuremultiplied byLth'etime ofexp,osure, andras the Weight of {radioactive fission r products is :proportional; to :the amountstof 932 and; 94 3 formed,-- it; is convenient; to; separate the;- desired elements when.:. the combined amounts thereof. are ,minute, such as, for example,, ap proximately .02:%-- byvweight of theirradiated uranium. ,sto inel eneu rrad ate nium ,for, a suitable. pe iod o t me. the 93tzsglisiwnyrted m s n rely to 94 Because the fission products in general a'rehighly radioactive, it is 'preferred that these materials be removed; I V The'fissionproducts consist of a large number-0f elements which may be classified into two groups; a light group with atomic numbers from-3510 45; and 'aheavy group 'with atomic' numbers-from Sl to- 60. The'fissio'n products with which: we:- are particularly concerned. are those-shaving a half-life= ofw more: thannthree days .:since; they? remain ,in the ne utronrirradiated 'I'EaCtiOH IIIEISS' in substantialyquantities atlease-one month; aftemreaction;

These products are, chiefly radioactiveisotopes v of a Sr, Y; Z,.;.Cb,- and Ru ofthe group :of atomicmumbersfrom e b' t s avin ;i ieh ril dsnrniiqnaeifi 1 case1ofdownw r .Ifl who i olu io ithrcnglgn h ads bent.

l ca gel nddiat m Qus e rl Ice 2,855,269

n zlh ta h y mew b r' nerateds mmw ach othe or phosphate insoluble state z. a

- Inv e preliminary dsorp ion :st pras QWm n-;;t e* drawing; thereactionumassp resultinggfrorn the neutron, bombardment oft uraniurn (and contairling;v plutonurn;

fission pro duots and; uranium) is, ,d iss cl-vied; a nrt1ic ci n e sou pm L Si WQL Q Hfin adso bent nta n dr-i na lon qted clumn 1. Sincea-th Qlut-i n, o in wnmoreisuhst m aw i rs ifieren sw th o a t o i m heoads rb nsg su stanc srswille e s bi tn tratal r:- iy ers l w h-.r-many dsorbemsi. the order of adsorption and position of the adsorbfifi fiubg stance in ;the,.,column is dependent, uoonathea' d so'rpt'ion inity ither 111 i srrwillr .innthe e bo i her' yers of h se; aving l w fl ni ies,.. w e ei'twc, r,,.rnor ,substenc s feren yst eng hsnfhttract oniorr he a sorbent-me.treated. there willjhe antendencyfor the' substanccsto.. be ad; sor edins rat o layers enetalln 'pe i hew rd f f adsorp on, ipcsitinnhptltheiadsorbedisnbslanc ii i a column of adsorbent.isdflfindentnuponthe adsorptipn fiini yt fw he per ariad ba ayers/fin sorbates. haying i Aafli itiesnw l i;the, aseotdow w d .flbw f o n throughllieradsjcrb' nt I dSQfgtiQllz toniurn from] products;

If the original sol length of time through 'thead'sorbe t var f s e mat a be ome pro r. s e -y 0 eretllmit e o w rdflbw' 's t q ml ecolumm Ill-D8. co u n r r na rha i han p'peri eret fims nbd; P t idd e aye o .,fi fproductsl, antlial" ye of an um,may,, con; on rstt uhstantialu of. all; ers ,of plutonium andj fission pi;odncts, an finall o yrag ia e layer 'p u pn p a dthat adv n age wi resu ttrqm nu ess to any one ofgtheseth'ree stagesjnjplg ng e a sired s pa a cn o emcy a one. 9 '11:: theme; n men n d,n ndyl onsequentl allln us lmodifial-i. tions e ons d i ome hin. t e sccner fltheririe vent ion r,

uch chromatographic abs rp er:v o he. s paration substances present in fsolntion of m trondrrzadiateduranium may he car; d f outgwith 1a wideiva-rietyaofgado be ts, inc oth q e, .a sorhentser uch' a e d reen clad bnat d.,carbnnacecus an. t na sed" a considerable bonisulnh ent s-su'chas activ'a ma erialfleo-r a bl ndp enolwformal ehyderesin; pref:

Patented Oct. 7,1958

asst-5,269

larly advantageous results are obtained in the first portion of the process by the use of ion exchange adsorbents, in which the cation of the adsorbent is exchanged fora similarly charged ion of the substance to be adsorbed. It has been found that the process is particularly effective when the adsorbent used is a relativelyinert organicma- Thus, the adterial containing sulphonic acid groups. sorbent may comprise phenol-formaldehyde resins, lignite, phenol-tannic acid resins, or the like, which contain numerous. R-SO -R' groups, in which R is an organic group'and in which R is hydrogen or a metal ion, although R is preferably Hr orNar. A' satisfactory adsorbent for use in column 1 is a phenol-formaldehyde condensation product-containing such sulphonic' acid groups; In the adsorptionprocess, the hydrogen or other cation of the sulphonicacid group is replaced by a cation ofthe substance to be adsorbed and thereby forms a more or less loosely associated molecule-with the residue. The following is an example of a method by which a sulphonated resin may be pre ared. One hundred and seventy-five parts of l-hydroxybenzene-4-sulphonic acid are heated together with 40 parts of a formaldehydesolution of30% strength for one-half hour to about 105 C. Then, further 60 parts offormaldehyde areadded and the temperature is kept for about .ten hours at 90 C. i A hardblack resin is formed which is stable to water and of conchoidal fracture. This resin is washed with water and ground to a powder. By regeneration with an acid or a solution of common salt, after'use for adsorption, the base-exchanging body regains its original adsorption capacity.

It is preferred that the amount of adsorbent in column 1 should be in direct proportion to the quantityof uranyl nitrate hexahydrate'solution to he run through the column. When plutonium is to be removed from uranium, fission products, and the like, it has been found desirable that for each pound of uranyl nitrate hexahydrate at least approximately 0.15 pound of the sulphonated phepol-formaldehyde resin be used. A proportion that has been found to be particularly suitable is 0.19 pound of the sulphonated phenol-formaldehyde resin for each pound of the uranyl nitrate hexahydrate.

The overall rate of adsorption of the plutonium, uranium, and fission products is generally dependent 'upon the particle size of the adsorbent in that more finely di-' vided adsorbents will give an increased adsorption when the plutonium 'is in contact with the. adsorbent for only a shortjperiod of time. Thus, a sulphonated phenolformaldehyde resin of average particle size of 30 mesh will give only 75% adsorption as compared'to the adsorp- 4 adsorbates movingdown the column in .acontinual process of desorption, readsorption, and desorption with the wash solution or solutions. As the uranium is desorbed and passes down the column, the other adsorbates are also desorbed and likewise pass"; down the column, although at. lesser rates.. As each componentrreaches the bottom of the column, it passes out with the wash solutions and may be collected as a separate fraction.

The wash solutions A, B, or C contain cations exchangeable for the ions to be desorbed. It will be understood that they will be effective to, remoie adsorbate from the adsorbentuntil such'time as substantial equilibrium is reached between theratesrof desorption and readsorption of the particular cation or cationsbeing desorbed. While the dissolved adsorbate may be readsorbed along the column, further amounts of wash solution will again desorb the substances; this will 'continue until the adsorbate passes out of the column.

In the case of plutonium, fission products, and uranium, it has been found that aqueous solutions of acids are particularly suitable because of the speed of desorption and the relatively small amounts of wash solution required, probably due to their high degree of dissociation. Aqueous solutions of acidforming substances as, for -example, mineral'acids such as H 80 HCl, or HNO or acid salts such as NaHSO in varying concentrations have been used satisfactorily.

As some of the components present in the original solution may have similar adsorption afii nities, one or more adsorbates, such as some of the fissionproducts, may overlap in the layers above and below any given layer. When such adsorbates are removed, the fraction cont ining any one adsorbate as the predominant adsorbed constituent may also contain moderate amounts of the adsorbates of the layersabove and/or below. Thus, the uranium fractions S and A may contain moderate amounts of fission products, the fission products fraction B may contain a negligible amount of plutonium, and

the plutonium fraction C may contain moderate amounts tion of 100-200 mesh resin when the plutonium is in contact with the adsorbent for ten minutes. When thetime of contact is two hours, the 'difiere'nce between amounts adsorbedis negligible. t

f To facilitate the formation of layers or strata of adsorbed substances,icolumn 1 is preferably of relatively small diameteror cross-section in proportion to its length- The bottom of the column is constructed. to permit the passage'pf the solutionstherethrough while retaining the adsorbentfthereon. .Tightly Iwoven metal screens, glass wool,andthe like may bejemploye'd for this purpos'e. The adsorbentis loosely. packed in the'column with its bed depthadjustedtothenumber and amounts of adsorbates in the solutionto betreated. The particle size of the'adsorbent is important in that the smaller the particle size, the more rapid the rate of adsorption, although the adsorbent must not beso fine as to greatly impede the rate of flow of the solutions through the .column. When ion-exchange resins ofthe sulphonated phenolformaldehyde typeare used, .a particle size of between of fission products.

To further separate and purify the partially separated substances, the various fractions obtained from column 1 maybe treated with adsorbents. The uranium fraction will comprise the original solution 8' from column 1 containing a substantial amount of unadsorbed uranium and the first wash solution A containing a substantial amount of desorbed uranium. This uranium fraction is furthertreated'in column 2. The fission products fraction Bf requires no furthertreatment as it consists for the most part only of fission products. The plutonium fraction C is further treated in column 3 to decontaminate the plutonium, that is, to remove radioactive fission products. 1

' The uranium fraction consisting of fractions 8' land A contains substantially all of the uranium, moderate amounts of fission products, and a negligible amount of plutonium. The uranium and fission products are separated from each other by passing fractionsS' and A, either together or separately, through column 2 containing a cationexchange resin which may be similar to or diiferent from that'used in column 1. In column 2, the amount of adsorbent used may be increased considerably; It has been found that atleas t 1.02 pounds of adsorbent to 1 pound of the original uranyl nitrate hexahydrate solu-.

tion is satisfactory. When 3.31 pounds of adsorbe ntis adsorption in column 2 are similar to thoseofcolumnl. As fractions 8' and. A pass through the adsorbent, a substantial amount of the uranium is adsorbed with the remainder passing out of'colurnn 2 with the solutions which are collected as fraction SA. Negligible amountsj of fission products having beta and gamma activity (refer-red to hereinafter as beta activity" andgamma ac tivity," for brevity) pass oute t the column with the un-V slso edpr niumt I n; 2 is washed with an acid Wash solution D which will removet substantially all "-of the adsorbed uranium together with negligible amounts of fission products, o form fraction D. Fractions SA 'and D' containing substantially all of the purified-uranium may be combined to formvtlieufinal urahiilfi ufraction U, 7 'A second-acidwash solutionE adapted primarily to remove fissionproducts may lbe fiowed I through a column 22 remove moderate amountsof-fission products from the adsorbentz- Solution-E---wit-h theT-desorbed fissionproducts is collected as fraction E5.

, I The plutonium fraction obtained from the first adsorp tion stepslcontains substantially all of the plutonium togethez-with-moderate-amounts of fission products. To further separate and; purify the plutonium, solution C is flow jath'r ug column-3 containing--anadsorbent-whose anion 'fo'rihs cluble surface compounds with the plutonium. Such'l adsorbents-- comprise 1 compounds of lowsolubil tha'ving' afg'monomeric or soluble anion and includeznconiurn phosphate and"barium iodate. The

plutonium'may be recovered using other adsorbentssuch coluni'ii 1.3,. Ofgthse, zirconium phosphate isvery' satis eetcryflwhenu c r e L v c lumn. in t e a pr x r t of 0.0027 pound for eachpound of the original uranyl nitratehexahydrate in the solution S. Where 4 grams of zirconium phosphat fis used, the rate of flow of solution C is preferably from to ml. per minute for each f b i r nu., H .7 r

' o n met od PFWQWfiQR of e;

ate, a zirconium salt solution, for exe a nsz rwnium n rate i de s'phoric acid thereby obtaining a prei co um. uh srhate v o ns e; against-the-presence of zirconyl phosphate in the precipitate; it 'is preferred-to-digest-theprecipitate in the -pres-- nceeotnitr' eaeidti r xamp e soluticnbeingibetween,;2 M,and;,4 M;in HNQ at 90 C. to 100. C.,fo r. approximatelyonehour toconvert thezirconyl phosphate tQoZircQnilmPhosphate. When it is ,desired to .obtain the rcon um ruho pha e 1 n ne t: pport a e al uch use-g ass, w oln l ic t Powder clas di e t o of the:iini,t,ial {precipitate to, convert-substantially al er this" precipitate ,torzirconium; phosph ey ay e i cne jn the presence of the inertsupportiug materiallher by causing-t e rc n um pho phat o. a er firmly m u ner l upnu ti g m ter al-1 o i As ,;soluti o n,.;C{ flows; through, ,the zirco nium phosphate column, substantially all of the plutoniumis, adsorbed while most of the fission products pass through;the :adsorb ent and outloflthc, column; they-may,becolleeted as fraction C117. An acid awash solution F adapted primarily m remove. fission produets s pa e th o gh; co umn 3 to remove; .as .mucheof, the absorbed ;;fission;.,products ,as. possiblesand: isrthen collected asnfractionF. The: two frac; tio'ns CiTand F :"constitute :the xfissionzproducts fraction from the zirconium phosphate '1 column. To. remove the plutonium; wash-solution Giconsisting of a single :acid aiid adaptedprimarilyto-remove plutonium is passed through the column; it removes substantially I all ;of the plutonium together, Withnegligible amounts of-fission 2 t i' o termu i t Pue .I'Fissic'rip uets 'fra'ctionsB, .B, C'. ndh y be combinedltoforml the ,final fission products. fraction ,FPg PI rum rriacusnrurmm column 3 contains ,substan:

tial a lioft e cla fi d ph wn u i 4' l n onmcmhodiment, oji -the inventiqnneutron-irradiated ridi sclv qu in;- nitric cid; too-form Solution ,8

which h as 0%AselutiQnFcf urarlyl tr t hezsahy lra haying-a pH value ofgb e tween'l'andtii v j f l .le'r sti lfiow dt r ug a fiiiel d vided adsorbent contalricd 'iui cyli udricaltcoll umn lwhichi's approximately 7 cm. in'diameter'and f. the f u henat 'dlphenq si m ld "hy adsorption ini columm 1 the arnountjo resin used ,is'

PEif l blY, -2.271J9und"for1 each; poundlofi the ,tiranyl nitrate ,hexahydrate in liters of solution, 2,107 liters of solution; sra yj t 8 m v e qlut cn: ,7 tant flllv.. ll f; the plutonium ucts, and'a small :amounmr th ur A la seemeum ,Q t hefw i I Y l n butfpa fsesz u 'wi it z tion'Sf. I"

To remove :thg' adsorbed washj solution A,

comprising 025 TM HQSQ; in-th 'el amoun of '9 .6'liters lis,. flowedithrough,thecolumn, The wash solutionfl A re-l moves the adsorbed unanium and carries,it o 1 1 t of, the.v column (to form fraction A't As Ihe uraniumhisgdes c rb,erd ,bysolution A,,the othe laye s ofr" ;ads batesxare. also desorbedand aregmoved'dqwrl the column.

Fractions S and A contain substan ally, all .0,f the uranium presentimsolution Sftogethe ith moderate, mo t of fis nlpr i stsand' s ef mquntr p u um; h se. r et q satecet: f e rf reat-i e urt h er rat hes rah uaxft ns; he c cn p od Present: y 7' To rem, 've fission productsfrom column 1, 'washsolu tion B comprising 2.15 lit ers ofja solution which is 10.16 3 2 4 and -1 M l B O} i q ed rousbi' blk, umn 1," A moderate offissiomnproducts is re moved by solution B together with .a minu'iegamount of plutonium to form fraction B; Fraction B mayqbe, considered as the fission products fraction 0f":CO11 1m 1 I"1 To remove i the plutonium, wash -solution=C comprising -1l.8 liters of -a solution which is 0I8 M in H PO1g and 'l M in HN0 -is flowed,through"column--13 Sub stantiallycall .ofathe plutonium is removed by wash solu-v tion C together .with modenate;amounts-:ofufission prod; nets to form fraction C. Fraction C may be considered as a plutonium fraction of column 1 and is reserved for further treatment to separat e ,the plutonium, from the fission products present.

To further sep arate the-uranium fromq the--fission prod-' nets-present in the uranium fractions S'mandtt A', these fractions are flowed "through column 2;,containing an adsorbent: similar to that used in column :1.: For column 2, theamount-of-resin used may be increased; one pound of the sulphonatedphenol iormaldehyde resinfon each pound of original urauylinitrateshexahydrate in the solution has been found to besuitable; Column 2 has a diameter of 20 'cm, andjattlengthiofjgl0-cmv-andconwins 7 a a-loa d orbents a r Fractions 8' and A are separately flowed through column 2 at a rate of 200 ml. per minute. A substantial amount of uranium is adsorbed while the remainder, together with a minute amountiof fission products, passes git ofrthe column with,,th ls itlll ionlto,,for111...fmcti0n To remove the ,1 adsorbed uraniumxfrom column 2,

wash;solution 'D comprising 35 liters of0J25 M H is flowed through the column. Wash.solutionuDuremoves. substantially all of the-adsorbeduranium together with minute amounts of "fission: products to form fractionDfi. FractionSA" and fraction D. constitute the purified uranium fraction" asvthey contain substantially all of' wash solution C and are contained in fraction C.

areseparated-from the'piutonium in column 3. Where 'from'column 2 as possible, wash sbliitionB comilr'isi s t I 42 1iters of 6 M HNOg is flowed through the column; itiremovesmoderateamounts of fission products to constitute fraction E'fthe fission productsoffraction of.

columrLZj" I TI'heI plutonium fraction Ci from' column 1 is .further treated to separate theplutonium from the 'moderate amounts of fission products present by flowing it through I column 3, The cylindrical column 3 is preferably 7 cm. in diameterand 8.5 cm. in length andcontains 0.004 kg..

the adsorbent at afrate'of 33 ml. per minute during which .timesubstantially' all "of, the .plutonium. is I adsorbed to;

' getherpwith moderateamounts '61": fission 'products. The

unadsorbedfission products pass..out of the column with the solution to form fraction'U'f from column 3.

.-.To remove theadsorbed plutonium from column 3,

wash solution G comprising 5.8 liters off7 M HNO is flowed. through the column; Substantially all of the plutoniumiis removed together with very small amounts offission products. to. form'fraction Pu- If desired; the step of removing fission products from I column. 11 as a separate fractionB may beomitted. In such case, the fission products that would otherwise be removed by wash solution B pass out. of column 1 with They use. of wash solution 'B is omitted,- the composition of in H PO and 2M in HN I 'Ihe-varioussolutions and their approximate composition with reference to'the drawing are summ'arizedin'.

the following tables. The percentages given in Tables II to VI are in terms of the respective materials contained in the original uranyl nitrate hexahydrate solution.

Table I Order 0! Quantity Flow Solution 0! thru 001- Solution,

umn #1 liters 1st Uolmoofit. p. +Pu+HNO3 42.00 2nd----- n s assassn a 4- 4th {1.0M in HNOL I Table II Order 01 Quantity Flow Solution of thru 001- Solution,

umn #2 liters sere e-t e a ac 1V1 y 1st 16.072 gamma activity-. 38'00 2.5% plutonium. ene a-r I e a as W1 A, 0 0'7; gamma activity 6 I 0 plutonium I D 3rd 0.25M H1504 35.00 E 4th 6.0M HNO; 42.00

F. I FractionsjC", and F contain the-fission- Products -Wash solution C is preferably changed from as'olution I 0.8 Min H P0 and l:M in HNO to a solutionOl M Tablelll V Order-of Flow 7 Solution i Solutiont; 1.

50.00 ,uranium." 0.95 -beta activity.

2.467%gamma activity.

0.17% gamma activity. 7

Solution 42 a gamma activity. i

{25% beta activity- 5% plutonium.

' Table VL Solution 27.50 beta activity. 21.40 gamma activity. 0.847 lutonium.

0.?(1 eta activity. 0.10 gamma activity:

015% plutonium. V I i 0.63%b9t580t1Yll2Y. Pu 0.61 gamma activity. 1 91.20%plutonlum;

I affect the adsorption characteristics of the adsorbent in the columns with respect to plutonium, uranium, and fission products to be later treated.

The above detailed description has been given for purposes of illustration and it is to be understood that the invention isto be limited only by the scope of the appended claims. I

We claim: I l

1. The method of separating plutonium from 'betaand gamma-active fission products and uranium in solution containing ions of a compound of plutonium in which the plutonium ions are in a tetravalent state and ions of compounds of betaand gamma-active fission products and uranium which comprises contacting said solution with a phenol-formaldehyde cation. exchange resin adsorbent to selectively adsorb said plutonium ions and at least a portion of said fission products including gamma-active fission products leaving a. substantial portion of ions of fission products and uranium in solution, then removing the solution fromthe cation exchange resin adsorbent and the adsorbed plutonium and fission products, thereafter forming another solution containing ions of plutonium and gamma-active fission products by redissolving the adsorbed fission products and plutonium from the cation exchange resin adsorbent with nitric acid, and then contacting the resultant solution with a zirconium phosphate adsorbent whereby said plutoniumions are preferentially adsorbed from solution leaving ions of gamma-active fission products in solution.

2. A process of isolating plutonium values from a feed solution containing said plutonium values in a maximum valence state of +4 together with uranium values and fission product values, comprising contacting said solution with a first adsorbent selected from the group consisting of phenol-formaldehyde resin, sulphonated phenolformaldehyde resin, phenol-tannic acid resin, lignite, silica gel and diatomaceous earth, whereby said plutonium values and part of said fission product values are adsorbed while said other part of said fission product values and the uranium values remain in solution; separating said adsorbent from said solution; contacting said adsorbent with an inorganic acid selected from the group consisting of sulfuric acid, hydrochloric acid, nitric acid, a dilute mixture of phosphoric and nitric acids and sodium bisulfate, whereby an eluate is formed containing said plutonium and said fission product values previously held by said adsorbent; contacting said eluate with a second adsorbent selected from the group consisting of zirconium phosphate, barium iodate, sodium aluminum silicate zeolite, sodium titanium silicate zeolite, sodium zirconium silicate zeolite and sulphonated phenol-formaldehyde resin having a higher degree of sulphonation than sulphonated phenol-formaldehyde resin used as said first adsorbent, whereby said plutonium values are preferentially adsorbed while most of said fission products remain in solution;

and removing said plutonium from said second adsorbent by contacting with a mineral acid.

3. The process of claim 2 wherein said feed solution is a nitric acid solution.

4. The process of claim 2 wherein said first adsorbent is a sulphonated phenol-formaldehyde resin and said second adsorbent is a sulphonated phenol-formaldehyde resin having a higher degree of sulphonation than said first adsorbent.

5. The process of claim 2 wherein said first adsorbent is sulphonated phenol-formaldehyde resin, the inorganic acid for elution of said plutonium values and said fission product values from said first adsorbent is a dilute mixture of phosphoric and nitric acids, said second adsorbent is zirconium phosphate and the acid for removing the plutonium values from the zirconium phosphate is nitric acid.

6. The process of claim 5 wherein the nitric acid for elution of the plutonium values from the zirconium phosphate has a concentration of about 7 M.

7. A process of separating plutonium values present in a maximum valence state of +4 in a nitric acid solution of neutron-irradiated uranium together with fission product and uranium values, comprising contacting said nitric acid solution with a sulphonated phenol-formaldehyde resin, whereby said plutonium values, part of said fission product values and a minor fraction of said uranium values are adsorbed on said resin; washing the resin with dilute sulfuric acid whereby said adsorbed uranium values are removed from said resin; contacting said resin with a dilute mixture of phosphoric and nitric acids whereby the bulk of said adsorbed fission product values are removed from said resin; contacting said resin with a further quantity of a dilute mixture of phosphoric I and nitric acids whereby an eluate containing said remaining fission product values and plutonium values is obtained; passing said eluate containing the plutonium and fission product values through zirconium phosphate whereby said plutonium values are held by the zirconium phosphate while most of the fission product values remain in solution; contacting said zirconium phosphate with a dilute mixture of phosphoric and nitric acids whereby the adsorbed fission product values are removed from the zirconium phosphate; and contacting said zirconium phosphate with nitric acid of a concentration of about 7 M whereby said plutonium values are removed from the zirconium phosphate.

References Cited in the file of this patent UNITED STATES PATENTS Thompson et a1. Mar. 19, 1957 OTHER REFERENCES 

2. A PROCESS OF ISOLATING PLUTONIUM VALUES FROM A FEED SOLUTION CONTAINING SAID PLUTONIUM VALUES IN A MAXINUM VALENCE STATE OF +4 TOGETHER WITH URANIUM VALUES AND FISSION PRODUCT VALUES, COMPRISING CONTACTING SAID SOLUTION WITH A FIRST ADSORBENT SELECTED FROM THE GROUP CONSISTING OF PHENOL-FORMALDEHYDE RESIN, SULPHONATED PHENOLFORMALDEHYDE RESIN, PHENOL-TANNIC ACID RESIN, LIGNITE, SILICA GEL AND DIATOMACEOUS EARTH, WHEREBY SAID PLUTONIUM VALUES AND PART OF SAID FISSION PRODUCT VALUES ARE ADSORBED WHILE SAID OTHER PART OF SAID FISSION PRODUCT VALUES AND THE URANIUM VALUES REMAIN IN SOLUTION; SEPARATING SAID ADSORBENT FROM SAID SOLUTION; CONTACTING SAID ADSORBENT WITH AN INORGANIC ACID SELECTED FROM THE GROUP CONSISTING OF SULFURIC ACID, HYDROCHLORIC ACID, NITRIC ACID, A DILUTE MIXTURE OF PHOSPHORIC AND NITRIC ACIDS AND SODIUM BISULFATE, WHEREBY AN ELUATE IS FORMED CONTAINING SAID PLUTONIUM AND SAID FISSION PRODUCT VALUES PREVIOUSLY HELD BY SAID ADSORBENT; CONTACTING SAID ELUATE WITH A SECOND ADSORBENT SELECTED FROM THE GROUP CONSISTING OF ZIRCONIUM PHOSPHATE, BARIUM IODATE, SODIUM ALUMINUM SILICATE ZEOLITE, SODIUM TITANIUM SILICATE ZEOLITE, SODIUM ZIRCONIUM SILICATE ZEOLITE AND SULPHONATED PHENOL-FORMALDEHYDE RESIN HAVING A HIGHER DEGREE OF SULPHONATION THAN SULPHONATED PHENOL-FORMALDEHYDE RESIN USED AS SAID FIRST ADSORBENT, WHEREBY SAID PLUTONIUM VALUES ARE PREFERENTIALLY ADSORBED WHILE MOST OF SAID FISSION PRODUCTS REMAIN IN SOLUTION; AND REMOVING SAID PLUTONIUM FROM SAID SECOND ADSORBENT BY CONTACTING WITH A MINERAL ACID. 